Beach Mouse Pelt Map

By Mike Dickison 06/02/2013

UC San Diego biologist Hopi Hoekstra and her co-authors found that differences between the light-colored beach mice of Florida and their darker cousins can be traced to a mutation in just one gene—at least, it can for the beach mice in Western Florida. Eastern beach mice seem to have evolved their colour some other way. She produced this very nice graphic mapping coat colour and the frequency of light and dark alleles. Her colleague Bill Lynn drew the mouse pelts in Photoshop.

Doesn’t this lay out their argument well? You can read the story they’re telling right off the graphic, even without the surrounding text. I couldn’t resist making a few changes, of course, because I’m fussy:

  1. Fading back the thick black coastline and the black pointers, so the data stood out better
  2. Choosing colours for the mouse ranges that were a bit more similar
  3. Making the color of the pointers match the colour of the ranges (this is pretty subtle, I admit)
  4. Changing the circle fills from black to a more-intuitive dark brown—I used the eyedropper to pick the shade of brown from the darkest mouse
  5. Extending the coastline and range into adjacent states, and labelling the states, because not everybody in the world instantly recognises the shape of Florida
  6. Making the state borders a little different from the coastline; artificial divisions shouldn’t be as prominent as natural ones
  7. And, in a bit of typographic pickiness, raising the baseline of each “=” by half a point (because it needs to match the upper-case letters and numerals) and putting a thin space on either side (a thin space is one you have to delve into the special characters to find—it’s really only used for fussiness like this)


I notice it all looks very Edward Tufte now, with his patented Tufte beige, but that wasn’t the intention. The earth-toned color palette comes ultimately from the mice themselves.

If I were to do a serious redesign, my first suggestion would be to move the Oldfield mouse up into Georgia, so that it’s physically separated from the beach mice, and obviously situated inland while they’re in the ocean. Adding a key or a label to explain the two allele colors would be nice, and would almost remove the need for an explanatory caption. But I think the graphic tells the story pretty well as is.


There’s a nice popular article on the findings, and the original paper is:
Hopi E. Hoekstra, Rachel J. Hirschmann, Richard A. Bundey, Paul A. Insel, Janet P. Crossland. 2006. A Single Amino Acid Mutation Contributes to Adaptive Beach Mouse Color Pattern. Science, 313(5783): 101–104. 7 July 2006, DOI: 10.1126/science.1126121. (PDF)